WiseCalc

Simple Interest Calculator

Calculate simple interest on unchanged principal for whole or fractional years, without compounding or loan payments.

USD
USD0USD100,000
%
-100.00%20.00%
years
0 years50 years

Simple interest = principal × annual percentage / 100 × years, with unchanged principal and no compounding. Enter time in years; 0.5 years means six months. The monthly figure is the constant-principal accrual for one twelfth of a year, independent of the selected duration; it is not a monthly payment or an amount already earned. At zero time, total earned interest is zero. Signed rates are evaluated algebraically, so losses can exceed principal and imply a negative total; there is no zero floor. Deposits, withdrawals, loan payments, taxes, fees and calendar day-count rules are excluded.

Total Interest / Change
$5,000.00
Principal Plus Interest
$15,000.00
Accrual for One Twelfth of a Year
$41.67

Principal and Signed Interest

What Is Simple Interest?

Simple interest is calculated only on the original principal amount, unlike compound interest which also earns interest on accumulated interest. The formula is straightforward: I = P × r × t, where I is the interest, P is the principal, r is the annual rate, and t is the time in years.

Simple interest is commonly used for short-term loans, auto loans, and some personal loans. It is also used in Treasury bills and certain savings instruments. Because it does not compound, simple interest results in lower total interest compared to compound interest over the same period.

Frequently Asked Questions